1. Field of The Invention
This invention relates to deflection cells for laser beams, essentially for power laser beams, i.e. the controllable means which make it possible to deflect these beams at a given angle.
2. Discussion of The Background
In many fields, for example, telemetry and missile guidance, a laser beam, whose space-time coherence makes it possible to define a "small and immaterial line" over a relatively long path, is used as a reference element.
Actually, for example, for terrestrial missile guidance over distances on the order of several hundreds of meters, a "helium-neon" type laser generator of several milliwatts of power, for example, is used. The beam defined by this type of generator is fine enough to be used as a reference for guiding or telemetering, and the generator itself is small enough to make it possible to solve the problem posed by the obligation to perform orientation changes of the beam emitted, at times for large angle values. For this purpose, it is sufficient, for example, to mount the laser generator on a plate which can be moved by motors along two or three axes. This use gives the desired result, of course, but provided that the necessary angular displacement velocity is not very great.
In particular for terrestrial missile guidance having to move quickly, deflection cells have been made which are placed on the laser beam itself, at the output of the laser generator, and which are controlled, electrically, for example, as the acoustooptical static deflectors well known to one skilled in the art. The advantage of these types of deflectors is that they very quickly respond to the deflection orders which are given to them. They exhibit, on the other hand, a major drawback, namely, that of being able to only deflect low-power laser beams. Actually, in the case of the deflection of power beams, the deflectors are deteriorated very quickly by the laser beam itself, and, moreover, their effectiveness decreases when the deflection angle increases. In particular, the power of the deflected beam diminishes.